Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry,scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH2 induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the γ-Ce to α-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.

The authors report on Langmuir probe measurements that show that hydrocarbon surfaces in contact with Ar plasma cause changes of electron energy distribution functions due to the flux of hydrogen and carbon atoms released by the surfaces. The authors compare the impact on plasma properties of hydrocarbon species gasified from an etching hydrocarbon surface with injection of gaseous hydrocarbons into Ar plasma. They find that both kinds of hydrocarbon injections decrease electron density and slightly increase electron temperatures of low pressure Ar plasma. For low percentages of impurities (∼1% impurity in Ar plasma explored here), surface-derived hydrocarbon species and gas phase injected hydrocarbon molecules cause similar changes of plasma properties for the same number of hydrocarbon molecules injected into Ar with a decrease in electron density of ∼4%.

The discharge characteristics in high power pulsed plasma enhanced chemical vapor deposition is studied with the aim to characterize the impact of high power pulses (HiPP). Using a power scheme of combined HiPP and direct current(DC) to ignite the plasma discharge, and adjusting the HiPP/DC time-averaged power ratio while keeping the total power constant, the effect of the high power pulses was isolated from the total power. By monitoring the discharge current along with the optical emission from the plasma, it is found that the amount of available ions increased with increasing HiPP/DC ratio, which indicates a higher plasma density. Using carbon filmsdeposited from acetylene in an argon plasma as model system, a strong increase in deposition rate with higher HiPP/DC is observed. The increased deposition rate is ascribed to a more efficient plasma chemistry generated by the denser plasma.

The low-frequency oscillation characteristics of a Hall thruster were investigated by varying the dielectric wall temperature. Experimental results indicate that increasing the dielectric wall temperature can result in an increase in the amplitude of low-frequency oscillation and a slight decrease in its frequency. Physical analysis revealed that this change is related to the secondary electron emissions at different dielectric wall temperatures. The evidence suggests that this technique can serve as an effective way for future studies to examine how secondary electron emissions affect a discharging thruster.

The authors report a new delayering technique – gas-assisted focused ion beam(FIB) method and its effects on the top layer materials of integrated circuit (IC) device. It demonstrates a highly efficient failure analysis with investigations on the precise location. After removing the dielectric layers under the bombardment of an ion beam, the chemical composition of the top layer was altered with the reduced oxygen content. Further energy-dispersive x-ray spectroscopy and Fourier transform infrared analysis revealed that the oxygen reduction lead to appreciable silicon suboxide formation. Our findings with structural and composition alteration of dielectric layer after FIB delayering open up a new insight avenue for the failure analysis in IC devices.